UK home energy · editable tariff model

Heating cost calculator

Compare a gas boiler, direct electric heating and a heat pump against the same annual delivered-heat requirement. Replace every preset with the tariff and seasonal performance that apply to the property.

Worked answer: at 12,000 kWh of delivered heat using Ofgem's 1 July-30 September 2026 average Direct Debit unit rates, the energy-charge model gives about £977/year for a 90% gas boiler, £1,044/year for a heat pump at COP 3.0 and £3,133/year for direct electric heating. Standing charges are excluded until explicitly enabled.

Enter one heat requirement

Then edit rates and seasonal performance for each option.

Annual delivered heat (kWh)

Tariff preset

Include a full annual standing charge for each option. Leave off when the account remains in place regardless of the heating choice.

Gas boiler

Seasonal efficiency0.90 = 90%

Gas rate (p/kWh)

Standing (p/day)

Direct electric heating

Efficiency1.00 = 100% at point of use

Electric rate (p/kWh)

Standing (p/day)

Heat pump

Seasonal COPUse a project-specific seasonal value

Electric rate (p/kWh)

Standing (p/day)

Open method

How the calculation works

input energy = delivered heat ÷ seasonal efficiency or COP
energy charge = input energy × unit rate
total = energy charge + optional standing charge

A seasonal efficiency below 1 increases fuel input relative to delivered heat. A heat-pump COP above 1 reduces electrical input relative to delivered heat. These values are assumptions supplied by the user; the tool does not estimate them from appliance marketing data.

1. Establish heat demandUse bills or a separate building model; do not confuse fuel input with delivered heat.

2. Enter real tariffsReplace the dated GB averages with the unit rate and standing charge on the relevant tariff.

3. Keep the boundary explicitDecide whether the standing charge is additional, then retain the assumptions with the export.

Static worked data

Q3 2026 comparison table

The same 12,000 kWh annual delivered-heat requirement is used for every row. This is a reproducible example, not a forecast for a particular home.

System	Efficiency / COP	Unit rate	Input kWh	Energy only	With full standing
Gas boiler	0.90	7.33p	13,333	£977.33	£1,083.33
Direct electric heating	1.00	26.11p	12,000	£3,133.20	£3,341.94
Heat pump	3.00	26.11p	4,000	£1,044.40	£1,253.14

Worked CSV Tariff presets CSV Methodology JSON

Calculated annual heating energy charge for gas boiler, direct electric heating and heat pump — Original Inzonex calculation using the visible Q3 rates and assumptions. Standing charges excluded in the bars.

Sources and boundary

Ofgem's unit-rate page supplies the Q3 and announced Q4 average Direct Debit presets for England, Scotland and Wales. Ofgem's Q3 announcement confirms the active-quarter averages and explains that actual bills depend on consumption, region, meter and payment method. The performance values are editable examples, not Ofgem data.

Engineering learning

What this tool teaches

Inzonex Engineering Learning publishes this free worked calculator to separate delivered heat, purchased energy, tariff rates and fixed charges. Save the export alongside a quote so the comparison can be reproduced.

Open the calculator learning catalogue · Estimate fabric U-values · Check dew-point margin

Heating cost questions

How does the heating cost calculator compare gas, electric heating and a heat pump?

It divides the same annual delivered-heat requirement by each system's entered seasonal efficiency or COP, then multiplies the resulting input energy by the entered tariff. Standing charges are included only when you switch them on.

Should standing charges be included in a heating comparison?

Include a standing charge only when it is genuinely additional to the decision. If the home already keeps that electricity or gas account for other uses, excluding the shared fixed charge is often the clearer incremental comparison.

Are the Ofgem prices my actual tariff?

No. The presets are Great Britain average Direct Debit price-cap rates for the stated quarter. Actual unit rates and standing charges vary by region, payment method and contract, so replace the preset with the figures on your bill or tariff.

Does the lowest modelled annual cost identify the best heating system?

No. The comparison covers energy and optional standing charges only; it excludes installation cost, maintenance, hot-water performance, emitter upgrades, comfort, peak capacity and building-specific heat-loss checks.